CODEWITHSUNDEEP
c#.netwinapiusb
galford13x
galford13x

Reputation: 2531

Win32Api USB SetupDiGetDeviceInterfaceDetail fail

I am attempting to connect to a USB GPS device. I can successfully connect to the device if I manually create a file via CreateFile WinApi (using the path specified in Device Manager).

However, when I try to select the device through enumeration I fail @ the SetupDiGetDeviceInterfaceDetail call.

I have C code that works correctly, but my C# translation does not appear to work correctly. I have tried many variations with essentially the same results.

C Code that works

// Get enumerator handle for the specified ClassGuid
HDEVINFO theDevInfo = SetupDiGetClassDevs((GUID*)&GUID_DEVINTERFACE_GRMNUSB, NULL, NULL,
    DIGCF_PRESENT | DIGCF_INTERFACEDEVICE);

SP_DEVICE_INTERFACE_DATA theInterfaceData;
theInterfaceData.cbSize = sizeof(theInterfaceData);

// populate theInterfaceData which contains device class information
if (!SetupDiEnumDeviceInterfaces(theDevInfo, NULL, (GUID*)&GUID_DEVINTERFACE_GRMNUSB, 0, &theInterfaceData) &&
    GetLastError() == ERROR_NO_MORE_ITEMS)
{
  gHandle = 0;
  return;
}
// This is normally used to obtain the device path information using theInterfaceData obtained above
bool initialized = SetupDiGetDeviceInterfaceDetail(theDevInfo, &theInterfaceData, NULL, 0, &theBytesReturned, NULL);
// theBytesReturned = 83
theDevDetailData =
(PSP_INTERFACE_DEVICE_DETAIL_DATA)malloc(theBytesReturned);
theDevDetailData->cbSize = sizeof(SP_INTERFACE_DEVICE_DETAIL_DATA);

bool initialized = SetupDiGetDeviceInterfaceDetail(theDevInfo, &theInterfaceData, theDevDetailData, theBytesReturned, NULL, &theDevInfoData);

C#

[DllImport(@"setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern Boolean SetupDiGetDeviceInterfaceDetail(
    IntPtr hDevInfo,
    ref SP_DEVICE_INTERFACE_DATA deviceInterfaceData,
    IntPtr deviceInterfaceDetailData,
    UInt32 deviceInterfaceDetailDataSize,
    out UInt32 requiredSize,
    IntPtr deviceInfoData
    );

[StructLayout(LayoutKind.Sequential)]
public struct SP_DEVICE_INTERFACE_DATA
{
    public Int32 cbSize;
    public Guid interfaceClassGuid;
    public Int32 flags;
    private UIntPtr reserved;
}


// Get enumerator handle for the specified ClassGuid
IntPtr theDevInfo = SetupDiGetClassDevs(ref ClassGuid, (DiGetClassFlags.DIGCF_PRESENT | DiGetClassFlags.DIGCF_DEVICEINTERFACE));

SP_DEVICE_INTERFACE_DATA DevInterfaceData = new SP_DEVICE_INTERFACE_DATA();
DevInterfaceData.cbSize = Marshal.SizeOf(DevInterfaceData);

initialized = SetupDiEnumDeviceInterfaces(theDevInfo, IntPtr.Zero, ref ClassGuid, 0,
        ref DevInterfaceData); 
// I assume The DevInterfaceData is populated correctly as it matches the C Code
// And I've compared the values in memory and they match

uint bytesReturned = 0;
initialized = SetupDiGetDeviceInterfaceDetail(theDevInfo, ref DevInterfaceData, IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);
// I expect bytesReturned = 83 and initialized = true which is the value that is returned in the C Code
// Instead the value 162 is returned

Upvotes: 3

Views: 12106

Answers (2)

Hans Passant
Hans Passant

Reputation: 942090

Congratulations, it is working. You'll get a Unicode string, it's twice as long. And a FALSE return is correct. You just need to call Marshal.GetLastWin32Error() and verify that you got ERROR_INSUFFICIENT_BUFFER. Your C code is broken, probably because you forgot to initialize theBytesReturned to zero.

Upvotes: 4

galford13x
galford13x

Reputation: 2531

I believe I found the problem.

After poking around pinvoke.net, I found the following

// build a Device Interface Detail Data structure
 SP_DEVICE_INTERFACE_DETAIL_DATA didd = new SP_DEVICE_INTERFACE_DETAIL_DATA();
 if (IntPtr.Size == 8) // for 64 bit operating systems
     didd.cbSize = 8; 
 else  didd.cbSize = 4 + Marshal.SystemDefaultCharSize; // for 32 bit systems

Changing this in my code allows me to obtain the DevicePath properly.

Reference for those interested.

http://pinvoke.net/default.aspx/setupapi.SetupDiGetDeviceInterfaceDetail

Upvotes: 2

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